Claude Code v2.1.236/237: Prompt Cache Fix & Concise Mode
Claude Code received two major updates on August 19, 2026, with versions v2.1.236 and v2.1.237 bringing a combined 35 changes to the agentic coding tool. The releases include 4 new features, 3 security updates, 11 improvements, and 17 fixes, with particularly important changes for developers using Claude Code through LLM gateways or Bedrock deployments.
Key New Features and Improvements
Version 2.1.237 fixed prompt caching for sessions using an LLM gateway or custom base URL, addressing a critical issue that affected both cost and response speed for enterprise users. For those using Claude Code via Bedrock or an internal gateway, this is a fix that should impact both cost and response speed.
The most visible change across both versions is a built-in “Concise” output style that allows Claude to lead with results and skip preamble and narration, while doing the work just as thoroughly. Users can select it under Output style in /config, providing a streamlined interaction mode for developers who prefer more direct responses.
The environment variable ANTHROPIC_DEFAULT_MODEL has been added, which specifies the model that new sessions start with. This gives teams more control over default model selection, though manual model picks through the /model command still take precedence and persist across restarts.
Cross-Session Communication and Accessibility
The notify_when_idle feature has been added to cross-session SendMessage, allowing users to request that another session on the same machine send a single notification the next time it becomes idle (macOS / Linux). This opt-in, one-shot capability enables better coordination between multiple Claude Code sessions without polling overhead.
Accessibility improvements also feature prominently in v2.1.236. Screen reader support for transcripts has been added, with live announcements for responses, permission requests, errors, and state changes, as well as heading navigation per turn now available in the VS Code integration.
Security and Sandbox Enhancements
Multiple changes relate to permissions around sandboxes and auto mode, reflecting ongoing refinements to Claude Code’s security model. On macOS specifically, wildcard read-deny rules (e.g. **/.env) now take precedence inside allowed read regions, cover matched directories’ contents, and can’t be bypassed by renaming the denied file. This prevents potential workarounds that could expose sensitive environment files.
The update also addresses MCP v2 connections endlessly reopening the subscriptions/listen stream against servers that terminate long-held streams on a fixed timeout, improving reliability when working with serverless deployments and other infrastructure that uses timeout-based connection management.
Background Session Management
Version 2.1.236 enabled subagent forking by default, allowing subagents to inherit the full conversation and prompt cache. The update also introduced the ability to mention other Claude sessions directly by typing @ in the prompt, enabling Claude to use SendMessage for direct session-to-session communication.
Additional fixes address edge cases in background session handling, remote control functionality, and voice mode on native builds. The releases continue the rapid development pace that has characterized Claude Code throughout 2026, with 369+ releases tracked from v0.2.21 beta to v2.1.237.
Key Facts
- Release Date: August 19, 2026 (v2.1.236 and v2.1.237)
- Total Changes: 35 changes across 2 versions, comprising 4 new features, 3 security updates, 11 improvements, and 17 fixes
- Concise Output Style: New built-in output style that states results first and omits preambles and running commentary
- Prompt Caching Fix: Resolved caching issues for sessions using LLM gateways or custom base URLs
- Model Control: ANTHROPIC_DEFAULT_MODEL environment variable added to specify default model for new sessions
Sources
- Claude Code v2.1.236~v2.1.237 Major Updates – DevelopersIO
- Claude Code Official Changelog
- ClaudeCodeLog X Post on v2.1.237
- ClaudeDevs X Post on Concise Output Style
